Organic light-emitting device and method of producing the same

ABSTRACT

An organic light-emitting device and a method of producing the same, the device including a substrate; a first electrode layer on the substrate; an emission layer on the first electrode layer; an electron transport layer on the emission layer, the electron transport layer including first electron transport layers and a second electron transport layer between the first electron transport layers and the second electron transport layer including a lanthanide metal; and a second electrode layer on the electron transport layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2012-0054453, filed on May 22, 2012, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field of the Invention

Embodiments relate to an organic light-emitting device and a method ofproducing the same.

2. Description of the Related Art

Organic light-emitting devices are self-light emitting devices that emitlight when a voltage is applied thereto. Organic light-emitting devicesadvantageously have high luminance, excellent contrast, multi-colors,wide viewing angles, high response speeds, and a low driving voltage.

An organic light-emitting device has a structure including an organicemission layer disposed between an anode and a cathode. When a voltageis applied across the electrodes, holes are injected from the anode andelectrons are injected from the cathode into the organic emission layer.The injected holes and electrons undergo electron exchanges in adjacentmolecules in the organic emission layer, thereby migrating to oppositeelectrodes. An electron-hole pair recombined in a certain molecule formsa molecular exciton in a high-energy excited state. The molecularexcitons emit unique light when returning to a low-energy ground state.

SUMMARY

The embodiments provide an organic light-emitting device including anelectron transport layer that may block metal from diffusing from acathode into an emission layer.

An embodiment provides an organic light-emitting device including asubstrate, a first electrode layer on the substrate, an emission layeron the first electrode layer, an electron transport layer on theemission layer, wherein the electron transport layer may include firstelectron transport layers and a second electron transport layer betweenthe first electron transport layers, wherein the second electrontransport layer may be formed of or may include a lanthanide metal, anda second electrode layer on the electron transport layer.

The second electrode layer may include an Ag-rich alloy containing adominant amount of Ag.

The second electrode layer may include an alloy of Mg and Ag.

The second electron transport layer may include ytterbium (Yb) orsamarium (Sm).

A thickness of the second electron transport layer may be about 5 Å toabout 15 Å.

The electron transport layer may include 2 or more layers of the secondelectron transport layer.

The organic light-emitting device may further include an electroninjection layer between the electron transport layer and the secondelectrode layer.

The electron injection layer may include a lanthanide metal.

The first electrode layer may be an anode, and the second electrodelayer may be a cathode.

An embodiment provides a method of producing an organic light-emittingdevice that includes providing a substrate, providing a first electrodelayer on the substrate, forming a hole injection layer or a holetransport layer on the first electrode layer, forming an emission layeron the hole injection layer or the hole transport layer, forming anelectron transport layer on the emission layer, wherein the electrontransport layer may include first electron transport layers and at leastone second electron transport layer between the first electron transportlayers, wherein the at least one second electron transport layer mayinclude a lanthanide metal, forming an electron injection layer on theelectron transport layer, forming a second electrode layer on theelectron injection layer.

The second electrode layer may include an Ag-rich alloy containing adominant amount of Ag.

The second electron transport layer may include Yb or Sm.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will become apparent by describing in detail exemplaryembodiments with reference to the attached drawings in which:

FIG. 1 illustrates a schematic cross-sectional view of an organiclight-emitting device according to an embodiment;

FIG. 2A illustrates a transmission electron microscope (TEM) image of acathode portion before a high temperature evaluation of anlight-emitting device of which the cathode is formed of Ag;

FIG. 2B illustrates a TEM image of the cathode portion after the hightemperature evaluation of the light-emitting device of which the cathodeis formed of Ag; and

FIG. 3 illustrates a schematic cross-sectional view of an organiclight-emitting device according to an embodiment.

DETAILED DESCRIPTION

The embodiments will now be described more fully with reference to theaccompanying drawings, in which exemplary embodiments are shown. Theembodiments may, however, be embodied in many different forms and shouldnot be construed as being limited to the embodiments set forth herein;rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the exemplary embodimentsto one of ordinary skill in the art. In the drawings, thicknesses oflayers and regions are exaggerated for clarity. Like reference numeralsin the drawings denote like elements, and thus repeated description maybe omitted. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. Expressionssuch as “at least one of,” when preceding a list of elements, modify theentire list of elements and do not modify the individual elements of thelist.

FIG. 1 illustrates a schematic cross-sectional view of an organiclight-emitting device 100 according to an embodiment.

The organic light-emitting device 100 may include an anode 111, a holeinjection layer 121, a hole transport layer 122, an emission layer (EML)131, an electron transport layer 141, an electron injection layer 142,and a cathode 151 that are sequentially formed on a substrate 101. Theelectron transport layer 141 may include first electron transport layers141 a and a metal barrier layer (hereinafter, referred to as, “a secondelectron transport layer”) 141 b between the first electron transportlayers 141 a.

The substrate 101 may be a substrate commonly used for organiclight-emitting devices. For example, a glass substrate or a transparentplastic substrate may be used as the substrate 101 in view of excellentmechanical strength, thermal stability, transparency, surfacesmoothness, ease of handling, and water resistance. The substrate 101may be formed of an opaque material such as silicon, stainless steel, orthe like.

The anode 111 may be formed on the substrate 101. The anode 111 may beformed of a material with a relatively high work function. The anode 111may be formed of a transparent conductive oxide, e.g., indium tin oxide(ITO), indium zinc oxide (IZO), zinc oxide (ZnO), Al-doped zinc oxide(AZO), indium oxide (In₂O₃) or tin oxide (SnO₂), but is not limitedthereto. The anode 111 may be formed by a vapor deposition method or asputtering method.

The hole injection layer 121 may be formed on the anode 111. The holeinjection layer 121 may be formed of, e.g., a phthalocyanine compound,such as copper phthalocyanine,N,N′-diphenyl-N,N′-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4′-diamine(DNTPD), 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine(m-MTDATA), 4,4′4″-tris(N,N-diphenylamino)triphenylamine (TDATA),4,4′,4″-tris{N,-(2-naphthyl)-N-phenylamino}-triphenylamine (2T-NATA),poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS),polyaniline/dodecylbenzenesulfonic acid (Pani/DBSA), polyaniline/Camphorsulfonicacid (Pani/CSA), polyaniline/poly(4-styrenesulfonate)(PANI/PSS), or the like, but is not limited thereto.

The hole injection layer 121 may be formed using a suitable method,e.g., by vacuum deposition, spin coating, casting, Langmuir-Blodgett(LB) deposition, or the like.

When the hole injection layer 121 is formed using vacuum deposition, thedeposition conditions may vary according to a compound used to form thehole injection layer 121 and desired properties of the hole injectionlayer 121. For example, the deposition conditions may include adeposition temperature of about 100° C. to about 500° C., a vacuumpressure of about 10⁻⁸ Torr to about 10⁻³ Torr, and a deposition rate ofabout 0.01 Å/sec to about 100 Å/sec.

When the hole injection layer 121 is formed using spin coating, thecoating conditions may vary according to a compound used to form thehole injection layer 121 and desired properties of the hole injectionlayer 121. For example, the coating conditions may include a coatingspeed of about 2,000 rpm to about 5,000 rpm, and a thermal treatmenttemperature of about 80° C. to about 200° C., wherein the thermaltreatment is performed to remove a solvent after coating.

The hole injection layer 121 may have a thickness of about 100 Å toabout 10,000 Å, e.g., about 100 Å to about 1,000 Å. When the thicknessof the hole injection layer 121 is within such a range, the holeinjection layer 121 may have satisfactory hole injection characteristicswithout a substantial decrease in driving voltage.

The hole transport layer 122 may be formed on the hole injection layer121. The hole transport layer 122 may include, e.g., a carbazolederivative, such as N-phenylcarbazole or polyvinyl carbazole, atriphenylamine-based material, such asN,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine(TPD), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB),4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), or the like, but is notlimited thereto.

The hole transport layer 122 may be formed using a suitable method,e.g., by vacuum deposition, spin coating, casting, LB deposition, or thelike. When the hole transport layer 122 is formed using vacuumdeposition or spin coating, the deposition or coating conditions mayvary according to a compound used to form the hole transport layer 122,and may be substantially the same as those applied to form the holeinjection layer 121.

An example of a material used to form the hole transport layer 122 mayinclude a carbazole derivative, such as N-phenylcarbazole or polyvinylcarbazole, a triphenylamine-based material, such asN,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine(TPD), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB),4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), or the like, but is notlimited thereto.

The hole transport layer 122 may have a thickness of about 50 Å to about1,000 Å, e.g., about 100 Å to about 800 Å. When the thickness of thehole transport layer 122 is within such a range, the hole transportlayer may have satisfactory hole transport characteristics without asubstantial increase in driving voltage.

In an implementation, a hole functional layer may be formed instead ofthe hole injection layer 121 and the hole transport layer 122. The holefunctional layer may include at least one material selected from thehole injecting materials and the hole transporting materials listedabove. The hole functional layer may have a thickness of about 500 Å toabout 10,000 Å, e.g., about 100 Å to about 1,000 Å. When the thicknessof the hole functional layer is within such a range, the hole functionallayer may have satisfactory hole injection and transport characteristicswithout a substantial increase in driving voltage.

At least one layer of the hole injection layer 121, the hole transportlayer 122, and the hole functional layer may further include acharge-generating material, in addition to a known hole injectingmaterial, a known hole transporting material, and/or a material havingboth hole injecting and transporting capabilities, so as to improve filmconductivity.

The charge-generating material may include, e.g., a p-dopant.Non-limiting examples of the p-dopant may include a quinone derivative,such as tetracyanoquinodimethane (TCNQ) or2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4TCNQ); ametal oxide, such as a tungsten oxide or a molybdenum oxide; and a cyanogroup-containing compound, but are not limited thereto.

If the hole injection layer, the hole transport layer, or the holefunctional layer further includes the charge-generating material,various changes may be made, e.g., the charge-generating material may beuniformly or non-uniformly dispersed in the hole injection layer, thehole transport layer, or the hole functional layer.

Subsequently, the EML 131 may be formed on the hole transport layer 122or the hole function layer using a suitable method, e.g., by vacuumdeposition, spin coating, casting, LB deposition, or the like. When theEML 131 is formed using vacuum deposition or spin coating, thedeposition or coating conditions may vary according to a compound usedto form the EML 131, and may be substantially the same as those appliedto form the hole injection layer 121.

At least one material selected from known light-emitting materials(including both hosts and dopants) may be used as a material for the EML131.

The host may include, e.g., tris(8-quinolinolato)aluminum (Alq3),4,4′-N,N′-dicabazole-biphenyl (CBP), poly(n-vinylcabazole) (PVK),9,10-di(naphthalene-2-yl)anthracene (ADN), TCTA,1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBI),3-tert-butyl-9,1-di(naphth-2-yl) anthracene (TBADN), distyrylarylene(DSA), E3, or 4,4′-bis(9-carbazolyl)-2,2′-dimethyl-biphenyl (CDBP), butis not limited thereto.

A suitable dopant may be used as the dopant. The dopant may include atleast one of a fluorescent dopant and a phosphorescent dopant. Thephosphorescent dopant may include an organic metal complex including Ir,Pt, Os, Re, Ti, Zr, Hf or a combination thereof, but is not limitedthereto.

Examples of red dopants may include Pt(II) octaethylporphyrin (PtOEP),tris(2-phenylisoquinoline)iridium (Ir(piq)₃),bis(2-(2′-benzothienyl)pyridinato-N,C3′) iridium(acetylacetonate)(Btp₂Ir(acac)), or the like, but is not limited thereto.

Examples of green dopants may include tris(2-phenylpyridine) iridium(Ir(ppy)₃), bis(2-phenylpyridine)(Acetylacetonato)iridium(III)(Ir(ppy)₂(acac)), tris(2-(4-tolyl)phenylpiridine)iridium (Ir(mppy)₃),10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]benzopyrano[6,7,8-ij]-quinolizin-11-one(C545T), or the like, but is not limited thereto.

Examples of blue dopants may includebis[3,5-difluoro-2-(2-pyridyl)phenyl](picolinato)iridium(III) (F₂Irpic),(F₂ppy)₂Ir(tmd), Ir(dfppz)3,4,4′-bis(2,2′-diphenylethen-1-yl)biphenyl(DPVBi), 4,4′-bis(4-diphenylaminostyryl)biphenyl (DPAVBi),2,5,8,11-tetra-t-butylperylene (TBPe), or the like, but is not limitedthereto.

When the EML 131 includes a host and a dopant, an amount of the dopantmay be generally selected within a range of about 0.01 to about 15 partsby weight, based on 100 parts by weight of the host, but is not limitedthereto.

The EML 131 may have a thickness of about 100 Å to about 1,000 Å, e.g.,about 200 Å to about 600 Å. When the thickness of the EML 131 is withinsuch a range, the EML 131 may have excellent light-emittingcharacteristics without a substantial increase in driving voltage.

When the EML 131 includes a phosphorescent dopant, a hole blocking layer(HBL) (not shown) may be formed between the hole transport layer 122 andthe EML 131 in order to help prevent diffusion of triplet excitons orholes into the electron transport layer 141. The HBL may be formed usinga suitable method, e.g., by vacuum deposition, spin coating, casting, LBdeposition, or the like. When the HBL is formed using vacuum depositionor spin coating, the deposition or coating conditions may vary accordingto a compound used to form the HBL, and may be substantially the same asthose applied to form the hole injection layer 121. The HBL may beformed of, e.g., oxadiazole derivatives, triazole derivatives,phenanthroline derivatives, or the like. For example, BCP may be used asa material of the HBL.

The HBL (not shown) may have a thickness of about 50 Å to about 1,000 Å,e.g., about 100 Å to about 300 Å. When the thickness of the HBL iswithin such a range, the HBL may have excellent hole blockingcharacteristics without a substantial increase in driving voltage.

The electron transport layer 141 may be formed on the EML 131. Theelectron transport layer 141 may include the first electron transportlayers 141 a and the second electron transport layer 141 b between thefirst electron transport layers 141 a.

The first electron transport layers 141 a may each include a suitableelectron transport material, e.g., Alq₃,2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP),4,7-diphenyl-1,10-phenanthroline (Bphen),3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ),4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ),2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD),(bis(2-methyl-8-quinolinolato-N1,O8)-(1,1′-biphenyl-4-olato)aluminum(BAlq), beryllium bis(benzoquinolin-10-olate (Bebq₂),9,10-di(naphthalene-2-yl)anthracene (ADN), or the like, but is notlimited thereto

The first electron transport layers 141 a may be formed using a suitablemethod, e.g., by vacuum deposition, spin coating, casting, or the like.When the first electron transport layers 141 a are formed using vacuumdeposition or spin coating, the deposition or coating conditions mayvary according to a compound used to form the first electron transportlayers 141 a, and may be substantially the same as those applied to formthe hole injection layer 121.

The first electron transport layers 141 a in sum may have a thickness ofabout 100 Å to about 1,000 Å, e.g., about 150 Å to about 500 Å. When thethickness the first electron transport layers 141 a is within such arange, the first electron transport layers 141 a may exhibitsatisfactory electron transporting characteristics without a substantialincrease in driving voltage.

In an implementation, each first electron transport layer 141 a mayinclude an electron transporting organic compound and a metal-containingmaterial. The metal-containing material may include a lithium (Li)complex. A non-limiting example of the Li complex may include lithiumquinolate (LiQ).

The second electron transport layer 141 b may be between the firstelectron transport layers 141 a. The second electron transport layer 141b may be formed of or may include, e.g., a lanthanide metal. In animplementation, the second electron transport layer 141 b may be formedof or may include, e.g., ytterbium (Yb), samarium (Sm), lanthanum (La),cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium(Ho), erbium (Er), or thulium (Tm).

Metal atoms of the cathode 151 may not pass through the second electrontransport layer 141 b, which may have a different lattice structure fromthe metal atoms of the cathode 151 or may have barrier properties. Thus,the second electron transport layer 141 b may help prevent the metalatoms, e.g., silver (Ag) atoms, from the cathode 151 from diffusing intothe EML 131 by passing through the electron transport layer 141.

The second electron transport layer 141 b may be formed, e.g., usingvacuum deposition. The second electron transport layer 141 b may have athickness of about 1 Å to about 20 Å, e.g., about 5 Å to about 15 Å.When the thickness of the second electron transport layer 141 b iswithin such a range, the second electron transport layer may helpprevent diffusion of the metal atoms from the anode 111 into the EML 131without a substantial decrease in driving voltage.

The electron injection layer 142 (for facilitating injection ofelectrons from the cathode 151) may be formed on the electron transportlayer 141. In an implementation, the electron injection layer 142 mayalso be formed of or may include a lanthanide metal. The electroninjection layer 142 may be formed of or may include, e.g., Yb, Sm, La,Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, or Tm. In an implementation, theelectron injection layer 142 may be formed of or may include a suitablematerial for forming an electron injection layer, such as LiF, NaCl,CsF, Li₂O, BaO, or the like, but is not limited thereto. However, thediffusion of the metal atoms from the cathode 151 into the EML 131 maynot be sufficiently blocked by the electron injection layer 142 alone.

The electron injection layer 142 may also be formed using vacuumdeposition, i.e., like the electron transport layer 141. The electroninjection layer 142 may have a thickness of about 1 Å to about 100 Å,e.g., about 5 Å to about 70 Å. When the thickness of the electroninjection layer 142 is within such a range, the electron injection layer142 may exhibit satisfactory electron injecting characteristics withouta substantial increase in driving voltage.

The cathode 151 may be formed on the electron injection layer 142. Thecathode 151 may be formed of or may include an alloy with a low workfunction, e.g., may be formed of or include an Ag-rich alloy, i.e., analloy containing a dominant amount of Ag. For example, the dominantamount of Ag in the Ag-rich alloy of the cathode 151 may indicate thatan amount of Ag contained in the cathode 151 exceeds 50% of a totalweight of the cathode 151. The cathode 151 may be formed of or mayinclude the Ag-rich alloy, which may be an alloy of Ag with, e.g., Li,Mg, and/or Al. In an implementation, a content ratio (e.g., a volumeratio) of Mg to Ag may be about 1:5 to about 1:10, e.g., about 1:7 toabout 1:10. The cathode 151 may exhibit excellent current conductivity.Thus, an efficiency of the organic light-emitting device 100 may beimproved.

The cathode 151 may be formed, e.g., using vacuum deposition. Thecathode 151 may have a thickness of, e.g., about 20 Å to about 300 Å, orabout 50 Å to about 200 Å.

FIGS. 2A and 2B respectively illustrate transmission electron microscope(TEM) images of a portion of an Ag-containing cathode before and afterhigh-temperature reliability evaluation of an organic light-emittingdevice. A high temperature reliability evaluation was performed on anorganic light-emitting device including a stacked structure of anelectron injection layer LiF: Yb (codeposition) 20 Å/cathode Ag 185 Å ata temperature of 85° C. and humidity of 85% for 120 hours.

In FIG. 2A, a thickness of the cathode was 185 Å before driving theorganic light-emitting device at a high temperature. However, in FIG.2B, a thickness of the cathode was increased to 241 Å after driving theorganic light-emitting device at a high temperature. Without being boundby this theory, it is believed that the thickness of the cathode wasincreased due to diffusion of Ag of the cathode after driving theorganic light-emitting device at a high temperature.

The diffusion of Ag may undesirably cause particles and a short circuit,which is evident as the occurrence of dark spots. The dark spots may beformed at a low temperature as well as at a high temperature. As anamount of Ag contained in a cathode increases, more dark spots may beformed, and thus a rate of deterioration of an organic light-emittingdevice may increase.

However, if a thickness of an electron injection layer or an electrontransport layer is increased to help reduce and/or prevent diffusion ofAg, luminous efficiency may be decreased or driving voltage may beincreased. Thus, according to an embodiment, the electron injectionlayer 142 and the electron transport layer 141 (or 241) may serve as abarrier blocking such diffusion of metal, e.g., Ag, from the cathode.Thus, diffusion of Ag from the cathode into an emission layer may bereduced and/or prevented.

A capping layer (not shown) may be formed on the cathode 151 to helpimprove optical properties and to help maximize luminous efficiency. Thecapping layer (not shown) may be formed as, e.g., a metal oxide layer, ametal nitride layer, or a metal nitrate layer. The capping layer (notshown) may be formed of, e.g., MoOx (x=2 to 4), Al₂O₃, Sb₂O₃, BaO, CdO,CaO, Ce₂O₃, CoO, Cu₂O, DyO, GdO, HfO₂, La₂O₃, Li₂O, MgO, NbO, NiO,Nd₂O₃, PdO, Sm₂O₃, ScO, SiO₂, SrO, Ta₂O₃, TiO, WO₃, VO₂, YbO, Y₂O₃, ZnO,ZrO, AlN, BN, NbN, SiN, TaN, TiN, VN, YbN, ZrN, SiON, AlON, or a mixturethereof.

FIG. 3 illustrates a schematic cross-sectional view of an organiclight-emitting device 200 according to an embodiment. The organiclight-emitting device 200 of FIG. 3 is described in terms of adifference with the organic light-emitting device 100 of FIG. 1.

The organic light emitting device 200 of FIG. 3 is different from theorganic light-emitting device 100 in that an electron transport layer241 may include two vertically separated second electron transportlayers 241 b in or between the first electron transport layers 241 a. Astwo separate second electron transport layers 241 b are present in theelectron transport layer 241, the number of layers blocking metal atomsfrom diffusing from the cathode 151 is increased. Thus, diffusion of themetal atoms may be effectively reduced and/or prevented. In animplementation, the electron transport layer 241 may include three ormore separate second electron transport layers 241 b.

By way of summation and review, a cathode should have a low workfunction and an excellent current conductivity to facilitate electronsupply at a low driving voltage.

An organic light-emitting device according to an embodiment may beapplied to an organic light-emitting device of various structures, suchas an organic light-emitting device emitting monochromatic light, anorganic light-emitting device emitting light of different colors, or anorganic light-emitting device emitting white light.

A lanthanide metal layer may be included in an electron transport layerin order to reduce the possibility of and/or prevent metal atoms fromdiffusing from a cathode to an emission layer. Accordingly, theoccurrence of undesirable dark spots may be reduced, and thus, areliability of an organic light-emitting device may be improved.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby one of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

What is claimed is:
 1. An organic light-emitting device, comprising: asubstrate; a first electrode layer on the substrate; an emission layeron the first electrode layer; an electron transport layer on theemission layer, the electron transport layer including first electrontransport layers and at least one second electron transport layer,wherein the at least one second electron transport layer: is between thefirst electron transport layers, has a thickness of about 5 Å to about15 Å, and includes a lanthanide metal; and a second electrode layer onthe electron transport layer.
 2. The organic light-emitting device ofclaim 1, wherein the second electrode layer includes an Ag-rich alloycontaining a dominant amount of Ag.
 3. The organic light-emitting deviceof claim 1, wherein the second electrode layer includes an alloy of Mgand Ag.
 4. The organic light-emitting device of claim 3, wherein avolume ratio of Mg to Ag in the second electrode layer is about 1:5 toabout 1:10.
 5. The organic light-emitting device of claim 1, wherein theat least one second electron transport layer includes ytterbium orsamarium.
 6. The organic light-emitting device of claim 1, wherein theelectron transport layer includes two or more layers of the secondelectron transport layer.
 7. The organic light-emitting device of claim1, wherein the first electron transport layers each include Alq₃,2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP),4,7-diphenyl-1,10-phenanthroline (Bphen),3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ),4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ),2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD),(bis(2-methyl-8-quinolinolato-N1,O8)-(1,1′-biphenyl-4-olato)aluminum(BAlq), beryllium bis(benzoquinolin-10-olate (Bebq₂), or9,10-di(naphthalene-2-yl)anthracene (ADN).
 8. The organic light-emittingdevice of claim 1, wherein the first electron transport layers each havea thickness of about 150 Å to about 500 Å.
 9. The organic light-emittingdevice of claim 1, wherein the first electron transport layers eachfurther include a lithium complex.
 10. The organic light-emitting deviceof claim 1, further comprising an electron injection layer between theelectron transport layer and the second electrode layer.
 11. The organiclight-emitting device of claim 10, wherein the electron injection layerincludes a lanthanide metal.
 12. The organic light-emitting device ofclaim 1, further comprising at least one of a hole transport layer or ahole injection layer between the first electrode layer and the emissionlayer.
 13. The organic light-emitting device of claim 12, wherein thehole transport layer or the hole injection layer further includes acharge-generating material.
 14. The organic light-emitting device ofclaim 13, wherein the charge-generating material is a p-type dopant. 15.The organic light-emitting device of claim 1, further comprising a holeinjection transport layer between the first electrode layer and theemission layer, the hole injection transport layer having both holeinjecting and transporting capabilities.
 16. The organic light-emittingdevice of claim 1, wherein: the first electrode layer is an anode, andthe second electrode layer is a cathode.
 17. A method of producing anorganic light-emitting device, the method comprising: providing asubstrate; providing a first electrode layer on the substrate; forming ahole injection layer or a hole transport layer on the first electrodelayer; forming an emission layer on the hole injection layer or the holetransport layer; forming an electron transport layer on the emissionlayer such that the electron transport layer includes first electrontransport layers and at least one second electron transport layer,wherein the at least one second electron transport layer: is between thefirst electron transport layers, has a thickness of about 5 Å to about15 Å, and includes a lanthanide metal; forming an electron injectionlayer on the electron transport layer; and forming a second electrodelayer on the electron injection layer.
 18. The method of claim 17,wherein the second electrode layer includes an Ag-rich alloy containinga dominant amount of Ag.
 19. The method of claim 17, wherein the atleast one second electron transport layer includes ytterbium orsamarium.